1. Field of the Invention
The present invention relates to an active device array substrate and a fabricating method thereof. More particularly, the present invention relates to a thin film transistor (TFT) array substrate and a fabricating method thereof.
2. Description of Related Art
Currently, the multimedia technology has become very developed due to the advancement of semiconductor devices or display apparatuses. As to displays, liquid crystal display (LCD) having such characteristics as high image quality, high space efficiency, low power consumption, and no radiation has become the mainstream in the display market.
An LCD panel includes a thin film transistor (TFT) array substrate, a color filter substrate, and a liquid crystal layer between the two. Generally speaking, the TFT array substrate has a plurality of pixel structures arranged as an array, and the pixel structures of a conventional TFT array substrate have to go through at least 5 mask processes to be completed. The first mask process is to define gates, scan lines, and common lines, the second mask process is to define a channel layer, the third mask process is to define sources, drains, and data lines, the fourth mask process is to define a passivation layer, and the fifth mask process is to define pixel electrodes.
Moreover, each of the pixel electrodes covers one of the common lines to form a storage capacitor. Generally speaking, the higher the aperture ratio of the pixel structures is, the higher the luminous efficiency of the entire LCD is. The common lines may affect the aperture ratio of the pixel structures since they are located below the pixel electrode. To resolve this problem, transmissive conductive material such as indium tin oxide (ITO) may be adopted as the material of the common lines to improve the aperture ratio of the pixel structures. However, an additional mask process for defining the common lines is required when fabricating the common lines with conductive material, thus, the manufacturing cost is increased, and since the resistance of the conductive material is higher than that of conventionally used metal material, power consumption and accordingly signal distortion may be caused.